黄酮类化合物对肿瘤多药耐药调节作用的研究进展

多药耐药是临床上化疗失败的重要原因之一。黄酮类化合物存在于多种植物中,具有广泛的药理活性,对P-糖蛋白(P-gp)、多药耐药相关蛋白(MRP)、乳腺癌耐药蛋白(BCRP)等外向转运蛋白的抑制作用使其可能成为肿瘤多药耐药调节剂。文中分别对黄酮类化合物对ABC家族转运蛋白抑制作用的研究概况、作用机制以及构效关系进行综述,为肿瘤多药耐药抑制剂的开发和应用提供重要信息。     

紫杉醇及其相关化合物的研究进展

紫杉醇是近年来研究和开发出的化学结构新颖，作用机理独特的新型抗肿瘤药。本文根据民紫杉醇结构类似的２００多个紫杉烷类二萜化合物，按其骨架特征归纳为五大类，并对每一类的ＮＭＲ谱鉴别特征进行了描述；对紫杉醇的全合成和半合成，紫杉烷基二萜化合物的分析方法和构效关系也作了简要介绍。同时讨论了紫杉醇的来源问题。     

紫杉烷类多药耐药逆转剂的合成及其逆转耐药活性紫杉烷类多药耐药逆转剂的合成及其逆转耐药活性

目的设计合成一系列新型紫杉烷类化合物并进行逆转多药耐药肿瘤细胞耐药活性的筛选。方法以本所生物合成的紫杉烷，Sinenxan A为原料，合成了10个(I_1～7, II_1,2, III)新的紫杉烷类化合物，其结构经FABMS，2DNMR确证，并对多药耐药癌细胞进行了逆转耐药性的试验。结果9个(I_2～7,II_1,2,III)化合物对多药耐药的人口腔上皮癌细胞KB/V200，能够显著逆转其耐药性，增强抗癌药的活性，其中化合物I₂, I₃, I₄逆转活性明显好于已知对照药Verapamil。结论紫杉烷类化合物作为多药耐药逆转剂有较好的逆转耐药活性，值得进一步研究。     

紫杉烷类抗肿瘤药物制剂研究进展

紫杉烷类药物具有良好的抗肿瘤活性,然而其极差的水溶性却限制了临床应用。为了扩大紫杉烷类药物的应用范围,各种给药系统相继被开发。该文简要综述了现已上市紫杉烷类制剂和处于各研发阶段制剂的研究进展,展望了紫杉烷类抗肿瘤药物研究的方向。     

一种紫杉醇耐药基因的发现

紫杉烷类(taxanes)是临床上常用的抗癌药,通过作用于β-微管蛋白阻滞细胞周期而诱导细胞凋亡。已知当干扰紫杉烷与微管结合的突变发生或多药转运蛋白P-糖蛋白表达上调时,将产生紫杉烷耐药。最近,Cohn等发现了紫杉醇耐药基因(Txr1),该基因下调凋亡诱导蛋白血小板反应蛋白(TSP1)的分泌,引起紫杉烷耐药。基于功能分析,在对紫杉烷敏感的前列腺癌细胞M2182中筛选与紫杉烷耐药有关基因过程中,发现了基因Txr1,该基因从未被描述过,编码一种核蛋白,在紫杉醇耐药的M2182细胞中的表达上调5倍。利用小分子干扰RNA(siRNA)降低Txr1表达后,在有紫杉…     

噁唑烷酮类化合物的定量构效关系

目的 研究新型全合成抗菌药噁唑烷酮类化合物的定量构效关系.方法 计算118个噁唑烷酮类化合物的量子化学和分子连接性指数等描述符,用偏最小二乘(PLS)对其进行筛选,得到9个对抗菌活性有重要影响的分子描述符,然后分别用PLS方法和改进的人工神经网络(ANN)方法建立这些描述符及其抗菌活性之间定量结构活性关系的模型.结果 比较ANN模型与PLS模型的结果,证明了化合物结构与活性之间的非线性关系.结论 所建立的定量构效关系模型能有效地进行噁唑烷酮类化合物的最小抑菌浓度值的预测,为新药开发提供新的参考和思路.     

基于SGLT2受体蛋白的新型糖尿病药物的研究进展

目的钠-葡萄糖共转运蛋白2(SGLT2)是肾小管上负责将尿糖重新吸收为血糖的重要转运蛋白,对该蛋白的抑制可以使糖从血液中转移进入尿液。本文总结了目前各大药物公司在研的SGLT2抑制剂的构效关系及其临床研究进展。方法综述了近年来国内外相关报道,对O,C,N-糖苷类和非糖苷类SGLT2抑制剂的药理、药效和药代学进行讨论,并就其临床研究及开发上市状况进行概述。结果 SGLT2抑制剂的结构与其药理活性和代谢稳定性间的关系是该类药物研发的重点。结论 SGLT2抑制剂与降糖作用的构效关系,对开发新一代治疗糖尿病药物具有重要意义。     

P—糖蛋白介导的多药耐药逆转剂的构效关系

寻找高效、低毒、专属性的多药耐药逆转剂是肿瘤化疗中面解决的难题。但是由于其作用机制的本质仍不清楚，这一问题的解决很困难，鉴于Ｐ－糖蛋白的重要作用，研究其介导的多药耐药逆转剂的构效关系有助于揭示多药耐药性的产生及其逆转机制，设计理想的可用于临床的逆转剂，本概述了对多药耐药逆转剂构效关系研究方法的认识，总结了近来出现的一些逆转剂特定的构效关系，并介绍了这方面的研究状况。     

人参皂苷衍生化及其抗肿瘤构效关系研究进展

人参皂苷为三萜类化合物,其某些衍生物在抑制肿瘤细胞生长或转移、诱导肿瘤细胞凋亡和分化、逆转肿瘤多药耐药等药理活性方面强于人参中主要的原生皂苷,人参皂苷衍生物作为抗肿瘤药物具有研究价值和开发前景。本文对人参皂苷衍生化的方法、主要衍生物及其抗肿瘤构效关系进行归纳总结,为新的抗肿瘤药物研究和开发提供参考。     

新型14β-侧链紫杉醇衍生物的合成及构效关系研究

以生物合成得到的紫杉烷 sinenxan A为起始原料,合成一系列新的紫杉醇衍生物,以寻找高效低毒、抗瘤谱广、综合性能好的新一代紫杉醇类抗癌药,并进行构效关系研究。从半合成的紫杉烷中间体7出发,分别经5步和6步反应成功地合成了4位羟基和4位乙酸酯两类共8个新的14β 侧链紫杉醇衍生物,2位基团为苯甲酸酯、间氯苯甲酸酯、正戊酸酯和苯乙酸酯。将目标化合物连同已合成的2个14β-侧链紫杉醇衍生物进行了微管聚合试验和体外肿瘤细胞抑制试验。所有化合物在浓度为10μmol·L^-1时对微管无作用。在体外肿瘤细胞抑制试验中,大部分化合物显示边缘细胞毒活性。14β-侧链紫杉醇衍生物的构效关系与13α-侧链紫杉醇衍生物有所不同,2位脂肪酸酯与2位芳香酸酯活性相当,表明2位基团的改变对活性无明显影响。4位羟基衍生物的活性好于4位乙酸酯。     

Second generation taxanes: from the natural framework to the challenge of drug resistance

Taxanes represent the most important class of antitumor agents introduced in cancer therapy in the last decade. The first member of the family was paclitaxel, firstly isolated from Taxus Brevifolia and found active as antitumor agent at the end of 60's. In the mid of 90's, a semi-synthetic taxane derived from 10-deacetylbaccatin III was introduced and thereafter named as docetaxel. Taxanes act by inhibiting microtubule dynamics, thereby inducing the arrest in M phase and the consequent activation of the apoptotic program. Since target of taxanes is not directly the genome, they are effective alone or in combination with DNA-damaging drugs in tumors not responding to conventional chemotherapeutics, such as advanced breast and non small cell lung cancer. In this review we will cover the aspects of clinical applications of the currently used taxanes as well as the clinical problems related to their use. Taking into consideration such problems, new taxanes have been developed in order to extend the spectrum of taxane-sensitive tumors and several of them are currently undergoing clinical trials. Among these agents, a newly developed taxane (BAY 59-8862) appears particularly interesting for the fact that it shows excellent oral bioavailability and activity in tumors with inherent resistance to paclitaxel.     

Novel drugs targeting microtubules: the role of epothilones

Among the drugs targeting microtubule functions by interfering with tubulin subunits, epothilones represent a class of anticancer agents which recently entered clinical development. Although epothilones share mechanisms of action similar to taxanes, they have non-overlapping mechanisms of resistance; in particular, while overexpression of class III β-tubulin plays a major role in taxane resistance, epothilones display their highest efficacy in class III β-tubulin overexpressing malignancies. Three compounds belonging to this family (patupilone, ixabepilone and sagopilone), have been actively investigated in clinical trials, and some of them are at an advanced stage of development. This review provides a comprehensive analysis of the available literature on epothilones, focusing on their clinical development and potential as an additional weapon in the arsenal against tumors.     

Cell death induced by novel fluorinated taxanes in drug-sensitive and drug-resistant cancer cells

The aim of this study is to compare the effects of new fluorinated taxanes SB-T-12851, SB-T-12852, SB-T-12853, and SB-T-12854 with those of the classical taxane paclitaxel and novel non-fluorinated taxane SB-T-1216 on cancer cells. Paclitaxel-sensitive MDA-MB-435 and paclitaxel-resistant NCI/ADR-RES human cancer cell lines were used. Cell growth and survival evaluation, colorimetric assessment of caspases activities, flow cytometric analyses of the cell cycle and the assessment of mitochondrial membrane potential, reactive oxygen species (ROS) and the release of cytochrome c from mitochondria were employed. Fluorinated taxanes have similar effects on cell growth and survival. For MDA-MB-435 cells, the C₅₀ of SB-T-12851, SB-T-12852, SB-T-12853 and SB-T-12854 was 3 nM, 4 nM, 3 nM and 5 nM, respectively. For NCI/ADR-RES cells, the C₅₀ of SB-T-12851, SB-T-12852, SB-T-12853, and SB-T-12854 was 20 nM, 20 nM, 10 nM and 10 nM, respectively. Selected fluorinated taxanes, SB-T-12853 and SB-T-12854, at the death-inducing concentrations (30 nM for MDA-MB-435 and 300 nM for NCI/ADR-RES) were shown to activate significantly caspase-3, caspase-9, caspase-2 and also slightly caspase-8. Cell death was associated with significant accumulation of cells in the G₂/M phase. Cytochrome c was not released from mitochondria and other mitochondrial functions were not significantly impaired. The new fluorinated taxanes appear to use the same or similar mechanisms of cell death induction as compared with SB-T-1216 and paclitaxel. New fluorinated and non-fluorinated taxanes are more effective against drug-resistant cancer cells than paclitaxel. Therefore, new generation of taxanes, either non-fluorinated or fluorinated, are excellent candidates for further and detailed studies.     

Chemotherapy of breast cancer: are the taxanes going to change the natural history of breast cancer?

Among the novel chemotherapeutic drugs introduced in the last decade, taxanes have emerged as the most powerful compounds and results available to date suggest that they will be remembered in the future as the breast cancer chemotherapy of the 1990s. The two taxanes (paclitaxel, Taxol?, Bristol-Myers Squibb and docetaxel, Taxotere?, Rhône-Poulenc Rorer) share some characteristics, but are also significantly different both in preclinical profile and, most importantly, in clinical characteristics. The main clinical differences are related to their different efficacy-toxicity ratio in relation to dose and schedule; the differing integrability of paclitaxel and docetaxel in anthracycline-taxane containing regimens, secondary to major differences in pharmacokinetic interactions between each taxane and the anthracyclines, and; the potential differences in level of synergism between each taxane and herceptin (HeR2Neu antibody/trastuzumab, Genentech/Roche). In clinical practice, the taxanes are now standard therapy in metastatic breast cancer after prior chemotherapy, in particular anthracyclines, has failed. Their role in combination with anthracyclines in first-line therapy of advanced breast cancer is emerging and sheds new light on the potential role of taxanes in the adjuvant setting. However, the impact of taxanes on the natural history of breast cancer is yet to be defined, despite the trend of results suggesting that these agents have the potential for significant improvements in advanced and, most importantly, adjuvant therapy of breast cancer. The results of all completed or ongoing Phase III trials in first-line metastatic and the adjuvant setting will help determine if taxanes will further improve the outcome of breast cancer or not.     

Epothilones: novel microtubule-stabilising agents

The past few years have witnessed the regulatory approvals of the anticancer microtubule stabilising taxane drugs, Taxol® and Taxotere®, which are rapidly gaining acceptance as important antineoplastic agents with potential against numerous solid tumour malignancies. Despite a basic understanding of the biochemical target of taxanes dating back nearly 20 years, new classes of tubulin-binding microtubule polymerisation enhancers were only reported in the last two years. Epothilones and discodermolide are newly discovered compounds, which are structurally distinct from the taxanes, but which possess similar tubulin polymerising and cell biological effects. In the first studies reported, these compounds displayed similar or greater potencies than taxanes, and the epothilones may represent an advance over the taxanes in retaining toxicity against various taxane-resistant cell lines. This review summarises the data published on epothilones and discodermolide and proposes further steps that could establish these new classes of compounds as potential second generation microtubule polymerisation enhancers.     

Chemotherapy of breast cancer: are the taxanes going to change the natural history of breast cancer?

Among the novel chemotherapeutic drugs introduced in the last decade, taxanes have emerged as the most powerful compounds and results available to date suggest that they will be remembered in the future as the breast cancer chemotherapy of the 1990s. The two taxanes (paclitaxel, Taxol, Bristol-Myers Squibb and docetaxel, Taxotere, Rh?ne-Poulenc Rorer) share some characteristics, but are also significantly different both in preclinical profile and, most importantly, in clinical characteristics. The main clinical differences are related to their different efficacy-toxicity ratio in relation to dose and schedule; the differing integrability of paclitaxel and docetaxel in anthracycline-taxane containing regimens, secondary to major differences in pharmacokinetic interactions between each taxane and the anthracyclines, and; the potential differences in level of synergism between each taxane and herceptin (HeR2Neu antibody/trastuzumab, Genentech/Roche). In clinical practice, the taxanes are now standard therapy in metastatic breast cancer after prior chemotherapy, in particular anthracyclines, has failed. Their role in combination with anthracyclines in first-line therapy of advanced breast cancer is emerging and sheds new light on the potential role of taxanes in the adjuvant setting. However, the impact of taxanes on the natural history of breast cancer is yet to be defined, despite the trend of results suggesting that these agents have the potential for significant improvements in advanced and, most importantly, adjuvant therapy of breast cancer. The results of all completed or ongoing Phase III trials in first-line metastatic and the adjuvant setting will help determine if taxanes will further improve the outcome of breast cancer or not.     

Epothilones: novel microtubule-stabilising agents

The past few years have witnessed the regulatory approvals of the anticancer microtubule stabilising taxane drugs, Taxol and Taxotere, which are rapidly gaining acceptance as important antineoplastic agents with potential against numerous solid tumour malignancies. Despite a basic understanding of the biochemical target of taxanes dating back nearly 20 years, new classes of tubulin-binding microtubule polymerisation enhancers were only reported in the last two years. Epothilones and discodermolide are newly discovered compounds, which are structurally distinct from the taxanes, but which possess similar tubulin polymerising and cell biological effects. In the first studies reported, these compounds displayed similar or greater potencies than taxanes, and the epothilones may represent an advance over the taxanes in retaining toxicity against various taxane-resistant cell lines. This review summarises the data published on epothilones and discodermolide and proposes further steps that could establish these new classes of compounds as potential second generation microtubule polymerisation enhancers.     

Lapatinib and ixabepilone for the treatment of metastatic breast cancer

Breast cancer is the second leading cause of cancer death in women. Treatment options for advanced-stage disease, although numerous, remain suboptimal. Lapatinib and ixabepilone are two new agents approved by the United States Food and Drug Administration (FDA) in 2007 for the treatment of locally advanced breast cancer (LABC) or metastatic breast cancer (MBC). When added to the existing endocrine therapies-single--agent cytotoxic therapies and combination chemotherapy regimens--lapatinib and ixabepilone offer potential treatment strategies for disease that has become resistant to trastuzumab and the taxanes, respectively. Lapatinib is an oral dual tyrosine kinase inhibitor against members of the human epidermal growth factor receptor (HER) family (HER1 or epidermal growth factor receptor [EGFR], and HER2). It is indicated for combination therapy with capecitabine for the treatment of patients with HER2-overexpressing LABC or MBC whose disease has progressed after receiving previous treatment with an anthracycline, a taxane, and trastuzumab. Of note, lapatinib is the first FDA-approved tyrosine kinase inhibitor indicated for use in MBC. Ixabepilone, the first FDA-approved analog of the antimicrotubule agent epothilone B, is indicated as monotherapy for the treatment of LABC or MBC in patients whose tumors are refractory or resistant to anthracyclines, taxanes, and capecitabine. It is also indicated in combination with capecitabine for treatment of LABC or MBC that is resistant to anthracycline and taxane. Both lapatinib and ixabepilone are fairly well tolerated. The most common toxicities with lapatinib are diarrhea (65%) and hand-and-foot syndrome (53%), whereas peripheral neuropathy (62%), fatigue (56%), and neutropenia (54%) are most common with ixabepilone. Though the conventional standard end point of overall survival has not yet been assessed in clinical trials, these agents have been shown to improve surrogate markers of clinical benefit: progression-free survival and the related time to progression. Future clinical trials should focus on elucidation of optimal combination or sequential therapies, as well as patient-specific therapies based on tumor characteristics, such as biomarkers and tumor subtypes.     

Structural studies of taxol analogues for drug discovery

Background: The major mechanism of action of antitumor taxanes, including two clinically useful antitumor agents, paclitaxel and docetaxel, lies in their interactions with β-tubulin in microtubule polymers, leading to cell cycle arrest and apoptosis. However, owing to the technical limitations, the molecular interactions of ligands with the residues in taxane binding sites of tubulin as well as the conformations adopted by taxanes on binding are still not fully understood. Objective: This review focuses on the exploration of paclitaxel's interactions with tubulin, and the impact of such efforts on the drug discovery for new taxanes and microtubule stabilizing agents (MSAs). Methods: Data were identified through the search of Chemical Abstracts and PubMed databases for research articles and reviews up to April 2008. Conclusion: Based on a collection of information gathered from crystallography, 1D and 2D NMR spectroscopy (NOESY, ROESY, REDOR), and structural–activity relationship (SAR) by chemical synthesis and pharmacological assays, ‘opened’ or T-shape conformations have been predicted to be the biologically active ones in recent years, and confirmed by further SAR studies. Some more potent analogues than paclitaxel or simplified compounds with similar potencies to that of paclitaxel have been discovered. Structural studies of taxol analogues will continue to make great contributions to the rational design of taxanes and novel prototype MSAs for drug discovery.     

Taxoids: cancer-fighting compounds from nature

This review covers advances in the discovery, preclinical and clinical development of potential anticancer agents based upon the diterpenoid taxane skeleton. The anticancer properties of approved clinical agents of this class are not discussed, but the review documents how, 13 years post-approval of paclitaxel (Taxol), the base taxane structure is still utilized as the starting skeleton for molecules with improved pharmacological and toxicological properties. Paclitaxel may in fact be the first example of a 'tunable' anticancer agent. In addition, paclitaxel, and perhaps other taxanes in due course, has activities beyond the known antitumor indications, with an example being the use of paclitaxel-coated stents in cardiovascular therapies.